Grain-boundary-proximal hydroxyl defects in Pt-regulated inverse spinel high-entropy oxide enabling efficient CO₂ photoreduction

Achieving efficient photocatalytic performance for high-entropy oxides (HEOs) continues to pose significant challenge, primarily attributed to their intrinsically limited charge carrier mobility and sluggish surface reaction kinetics resulting from heterogeneous defect distributions. Herein, the new Pt-regulated inverse spinel HEOs with honeycomb-like architecture are developed employing a facile sol-gel technique. The doping of trace amounts of Pt in the octahedral B voids of the high-entropy (FeZnAlCoMn)₃O₄ can enables electronic structure optimization and regulates the grain-boundary-proximal hydroxyl defects, thereby improving CO₂ adsorption/activation capabilities, charge transfer and separation efficiency, and surface reaction kinetics. As a result, the optimal high-entropy 1.6%Pt-(FeZnAlCoMn)₃O₄ achieves 3.41 times average CO evolution rate of (FeZnAlCoMn)₃O₄ and stable operations for 4 cycles in the photocatalytic CO₂ reduction. This contribution provides novel insights into the targeted design and regulation of high-entropy oxides (HEOs) for efficient photocatalytic CO₂ reduction, thereby establishing a new paradigm for grain boundary defect engineering that can be extended to other application fields.